Miniature spotwelder



Feb. 28, 1967 J, W RYAN' ETAL 3,307,012

MINIATURE SPOTWELDER Filed April 1l, 1965 5 sheets-Sheet i FledvApril11, v196e;

RYAN ETAL 3,3(922012 MINIATURE sPoTwELDER 3 Sheets-Sheet 2 Feb. 28, 1967J. W. RYAN ETAL 3,307,012'- MINIATURE SPOTWELDER Filed April ll, 1966 5Sheets-Sheet 3 United States Patent Oiice 3,307,012 MINIATURE SPOTWELDERJohn W. Ryan, Bel-Air, Richard L. May, Manhattan Beach, and ManningCitron, Los Angeles, Calif., assignors to Mattel, Inc., Hawthorne,Calif., a corporation of California Filed Apr. 11, 1966, Ser. No.541,621 Claims. (Cl. 219-86) The present invention relates and moreparticularly to such a sive to manufacture and which to use.

Miniature spotwelders designed for home use by inexperienced operatorsare known. While generally satisfactory, such spotwelders do havecertain disadvantages.

One disadvantage resides in the fact that, as is the case with allspotwelders, the parts to be welded must be heated to a glow in the areato be welded resulting in sparks sometimes being given olf. Theseconditions are likely to surprise an inexperienced operator causing himto drop a red-hot piece of metal on the floor. This creates a safetyhazard which is greatly magnified when the spotwelder is being used in acarpeted room, as is often the case.

Another disadvantage with prior art miniature spotwelders resides in thefact that some of them are comparatively expensive to manufacture andcomplicated to operate.

Yet another disadvantage resides in the fact that some prior artminiature spotwelders will soon become inoperative through electrodeoxidation.

In view of the foregoing factors and conditions characteristic ofminiature spotwelders, it is a primary object of the present inventionto provide a new and useful miniature spotwelder not subject to thedisadvantages enumerated above and having spark arrestor and electrodemeans especially designed for making simple welds eliiciently, safelyand expeditiously.

Another object of the present invention is to provide a bus bar for aminiature spotwelder which connects a swingable electrode to thesecondary winding of a transformer in such a manner that the bus bar notonly carries current to the electrode, but also biases the electrode toa predetermined, elevated position upon removal of welding pressuretherefrom.

Yet another object of the present invention is to provide new and usefulelectrodes for a miniature spotwelder which are conductive even thoughthey may become oxidized during use.

A further object of the present invention is to provide an actuatinglever for a miniature spotwelder which not only lowers a swingableelectrode into engagement with workpieces on a fixed electrode, 'butalso exerts a modulated clamping pressure in proportion to the thicknessof the workpieces.

A still further object of the present invention is to provide easilyreplaced, long-life electrodes for a miniature spotwelder.

Another object of the present invention is to provide a new and usefulwire cutting and bending ldevice for a miniature spotwelder.

Another object of the present invention is to provide a spark arrestorfor a spotwelder which is penetrable by a workpiece while completelysurrounding the workpiece to hide the welding area from view.

According to the present invention, a miniature spotwelder is providedwhich includes a transformer having a primary winding and a secondarywinding. The transformer is designed to have a maximum rise of 60 C.,when operated as is intended. The primary winding operates on 117 voltsA C. and draws approximately 13 amperes at full load. The secondarywinding operates at to a miniature spotwelder Welder which is inexpeniseconomical and safe 3,307,012 Patented Feb. 28, 1967 1.7 volts at noload and at approximately 1.0 vol-t at' approximately 600 amperes.

A movable electrode is connected to the secondary winding by a bus barhaving sucient resiliency and a predetermined shape for biasing theswingable electrode to a predetermined position spaced sufficiently froma xed electrode that workpieces may be admitted between the electrodes.Both electrodes are made from a silverplated, copper-chromium alloy.'Ihe electrodes are silver plated because .the oxide of silver is almostas conductive as the silver. The bus bar for the swingable electrode ismounted inside an arm which is pivotally mounted on a housing. The armmay be pivoted by depressing'an actuating handle including a steel leverwhich is formed integrally with a crank member and a bight portion. Thecrank member is connected to the arm for swinging it when the lever isdepressed downwardly. The lever, when it reaches the bottom of itsstroke, actuates an electrical switch completing a circuit to theelectrodes. The switch is permanently alhxed to the welder in a positionsufiiciently below the lever so that it must ybe sprung downwardly afterthe electrodes have firmly clamped a workpiece to be welded. The amountthe lever is sprung for thick workpieces is greater than the amount itis sprung for thin workpieces. Thus, the operating handle has a torsioneffect which results in approximately the same p.s.i. being applied to athick piece as that applied to a thin piece.

The bus bar which connects the swingable electrode to the secondarywinding is made of hard-drawn copper and serves as a return springreturning the swingable electrode to its upper position.

A new and useful spark arrestor of the present invention is permanentlyconnected to each elect-rode. Each spark a-rrestor completely surroundsits associated electrode and not only arrests sparks, but also hides theelectrodes from view during a welding operation to prevent aninexperienced operator from becoming surprised by the appearance ofsparks which might cause him t-o drop a red-hot workpiece on the floorcausing damage thereto.

In addition, a new and useful wire cutting and bending device isprovided. This device may be readily attached to the housing of thespotwelder for use in combination therewith.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may best be understood byreference to the following description, taken in connection with theaccompanying drawings in which like reference characters refer to likeelements in the several views.

In the drawings:

FIG. l is an exploded, perspective view of a miniature spotwelderconstituting a presently preferred embodiment of the invention incombination with a new and useful wire cutting and bending device of thepresent invention;

FIG. 2 is an enlarged, partial cross-sectional view taken along line 2 2of FIG. 1;

FIG. 3 is an enlarged, partial wire cutting and bending deviceoperation;

FIG. 4 is an enlarged cross-sectional View taken along line 4 4 of FIG.l with parts shown in elevation;

FIG. 5 is a cross-sectional view taken along line 5 5 of FIG. 4;

FIG. 6 is an enlarged, partial cross-sectional view taken along line 6 6of FIG. 5;

FIG. 7 is a cross-sectional view taken along line 7 7 of FIG. 5;

plan view showing the during a wire bending FIG. 8 is a partialelevational view of the spotwelder of FIG. 1 with parts broken away toshow internal construction;

FIG. 9 is a partial cross-sectional view of the electrode portion of thespotwelder shown in FIG. 8 being taken at right angles thereto;

FIG. 10 is a schematic view showing a portion of a spark arrestor shownin FIG. 9 during one step in the manufacture thereof; and

FIG. 11 is a view similar to FIG. 10 showing the spark arrestor during asecond step in the manufacture thereof. Referring again to the drawings,a miniature spotwelder constituting a presently preferred embodiment ofthe invention, generally designated 101, includes a housing 12 having anupper housing half 14 and a lower housing half 16. The upper housinghalf 14 includes a closed top wall 18, a front wall 20, a rear wall 22,side walls 24 and an open bottom 26. The open bottom 26 is encompassedby a peripheral lip 28 for properly positioning the upper housing half14 on the lower housing half 16.

The top wall 18 is provided with a plurality of elongated openings 30adjacent the side walls 24 permitting the free flow of air from aplurality of louvers 32 provided in the bottom wall 34 of the lowerhousing half 16. The top wall 18 is also provided with a pair ofrectangular, recessed lands 36, 38 and a circular, recessed land 40which may be used for supporting suitable nameplates or other indicia.In addition, the top wall 18 is provided with a substantially squarerecessed portion 42 adapted to non-rotatably receive a wire bendingblock 44 for a purpose and in a manner to be hereinafter described.Also, a substantially rectangular recessed portion 46 is provided in thetop Wall 18 for receiving a wire cutter bar 48 having a rst notch 50provided along its lower edge 52, a second notch 54 provided along itsfirst side 56 and a third notch 58 provided along its other side 60. Thenotch 50 is adapted to engage a transverse web 62 provided in the bottomof the recessed portion 46 and the notches 54 and 58 are adapted toengage pads 64 and'66, respectively, formed on a wall 68 of the recessedportion 46 during the forming of the upper housing half by a moldingoperation which also forms an elongated opening 68 (FIG. 2) in the topwall 18 subjacent each pad 64, 66. The openings 68 facilitate extendingsuitable means upwardly within a mold to form the pads 64 and 66 withoutIrequiring a second step in the molding operation.

During this molding operation, an island 70 is also formed integrallywith the top wall 18 forming a housing for pivotally receiving the end72 of a swingable, electrode-holding arm 74. In addition, a fixed,electrodeholder housing '76 is formed integrally with the front wall 20during the molding operation and a U-shaped slot 78 is provided in Ithefront wall 20 in alignment with a similar U-shaped slot 80 provided inthe front wall 82 of the lower housing half 16. Additionally, the rearwall 22 is provided with a notch 84 (FIG. 7) which cooperates with asimilar notch 86 formed in the rear wall 88 of the lower housing half 16for receiving a rubber grommet 90 carrying an electrical conductor 92which connects the spotwelder 10 to a source of electrical power.

A cored, hollow boss 94 is provided on each corner of the bottomy wall34 on the lower housing half 16 for the reception of suitablerubber-like foot pads 96 which prevent the spotwelder 10 from slidingaround on a work bench. The hollow interiors of the bosses 94 pierce theinner surface 98 of the bottom wall 34 on a reduced diameter forreceiving suitable wood screws, not shown, for permanently aiixing thespotwelder 10 to a Work bench. An upstanding pedestal 100 may be affixedto the inner surface 98 of the bottom wall 34 by screws 101 and carriesan upstanding pin 102 (FIG. 4) at its upper end 104 for a purpose to behereinafter stated.

The bottom wall 34 is also provided with a pair of apertures 106 whichcommunicate with associated hollow bosses 108 extending upwardly fromthe inner surface 98.

4 When the housing half 14 is placed lon housing half 16, the bosses 108are in alignment with similar bosses 110 depending from the top wall 18for the reception of suitable bolts 111 which may be inserted throughthe apertures 106 in the bottom wall 34 and threaded into engagementwith internal threads 112 provided in the bosses for securing thehousing halves 14 and 16 together.

A frame 114, having four corner posts like the ones shown at 116,depends from the under side 118 of the top wall 18 for supporting awelding transformer 120. The transformer 120 may be secured to the frame114 by suitable stove bolts 122 which pass through each corner oftransformer laminations 124 and threadedly engage an associated post116.

The transformer 120 is designed to have a maximum temperature rise ofapproximately 60 C. and includes concentrically wound primary andsecondary coils 126 and 128, respectively. Under full load, thetransformer 120 changes 13 amperes of 117 volt house current intoapproximately 600 amperes of about 1 volt welding current. The primarywinding 128 may be connected to such house current by the conduct-or 92which includes a first lead 130 having a first end 132 connected to oneside of a normally open, single-pole switch 134 and a second lead 136having an end 138 connected to one side of an automatic circuit breaker142. A lead 144 con nects the other side of the circuit breaker 142 tothe primary winding 126. The other side of the switch 134 is connectedby a lead 148 to the primary winding 126. The circuit breaker 142 may beof any suitable type which senses overloads in both heat and current.Such overloads cause circuit breaker 142 to open and stop the How ofcurrent; however, after a short time the circuit breaker 142 cools andresets itself automatically.

A flat, wide copper strip 152 extends from the secondary winding 128 andis connected to one end 153 of a copper bus-bar 154 by abolt-washer-and-nut assembly 156. The other end 158 of the bus-bar 154includes a narrow portion 160 which is engaged by a xed electrode holder162. The fixed electrode holder 162 is mounted in the housing 76 andincludes an internallythreaded, frusto-conical end portion 163 extendingup through an aperture 164 provided in the top wall 166 of the housing76. The electrode holder 162 also includes a passageway 166 extendingthrough the body portion 168 thereof for reception of the reducedportion 160 of the end 158. The xed electr-ode holder 162 is firmlyaffixed in electrical contact with the bus-bar 154 by a fixed electrode17 t) having a comparatively broad spherical tip 172, a wrench-engagingbody portion 174, an externally threaded end portion 176 and a bus-barengaging tip 178. The electrode 170 may be conveniently made from acopper-chromium alloy which is silverplated for taking advantage of theconductivity of silver oxide when the tip 172 becomes oxidized duringuse of the spotwelder 10.

The electrode 170 is surrounded by a spark arrestor 182 which ispreferably permanently affixed to the top wall 166 of the housing 76 byspinning-over the end 183 of the frusto-conical portion 163 of electrodeholder 162 against a dished plate 184 provided in the spark arrestor182. Since it is desired that the spotwelder 10 be safe to use in ahome, on a rug for example, sparks must not only be prevented fromleaving the area of the electrode 170, but must be kept from view of anoperator of the welder 10 at all times during a welding operation toprevent the operator from being surprised by the appearance of sparkswhich might cause him to drop a red-hot workpiece on the rug. With thisin mind, the spark arrestor 182 includes a plurality of looped tufts 186made of filament glass to resist the heat given off by sparks duringwelding operations. The tufts 186 must be penetrable by Va workpiece 187(FIG. 9) being welded while co1npletely surrounding the workpiece byflexing around it. It is necessary to form the tufts 186 with loopedends prevent the ends from a braiding away The looped ends 188 may beformed by stitching the tufts 186 as shown in FIG. 10 by using glassthreads 190. However, the looped ends 188 will take a substantiallycircular shape which will not satisfactorily prevent sparks from passingthrough the tufts 186. This may be remedied by giving the loops 186 asubstantially flat shape by sewing them together with cotton threads 192and then by firing the tufts 186 in suflicient heat to burn the cottonthreads away while tempering the loops 188 so that they will take a setin this substantially Hat shape, as shown in FIG. 1l.

This firing does not burn the threads 190 leaving them in place to bindthe ends 196 of tufts 186 together. These bound ends are then aixed toan annular collar 197 which also carries the plate 184. The tufts 186are then treated with a material containing graphite so that they willbe lubricated to minimize wear when they are brought into engagementwith the tufts 186 of an upper, identical spark arrestor 194 and theworkpiece 187, as shown in FIG. 9.

A flat, wide copper lead 198 connects the secondary winding 128 to oneend 200 of a hard-drawn copper bus-bar 204 having a crook 206 connectingthe end 200 to a straight portion 208 extending through the larm 74 toits end 210 where the end 212 of the bus-bar 204 includes a narrowedportion 214 to which a swingable electrode holder 216, which may beidentical to the fixed electrode holder 162, is affixed by a swingableelectrode 218 which, in turn, may be identical to the fixed electrode170.

The swingable electrode holder 216 includes a passageway 166 and afrusto-conical portion 163, both of which may be identical tocorresponding portions of the fixed electrode holder 162. The end 183 ofthe portion 163 may be spun over into engagement with the dished plate184 of the upper spark arrestor 194 to permanently ax it to theswingable arm 74.

The natural resiliency of the bus-bar 204 combined with its shape,including the crook 206, biases the arm 74 to the position shown in FIG.4 wherein the swingable electrode 218 is suiiiciently spaced above theiixed electrode 170 to permit insertion of workpieces, such as theworkpiece 187, between the electrodes 218 and 170. When the arm 74 isswung to overcome the bi-as of the bus-bar 204, in a manner to behereinafter described, the end 200 is prevented from moving by thepedestal 100 provided in the lower housing half 16. This is accomplishedby engaging the pin 102 in a dielectric tting 220 having a shank portion222 engaged in an aperture 224 provided in the end 200 and a head 226adapted to seat on the upper end 104 of the pedestal 100.

The arm 74 is swingably connected to the island 70 by a pivot pin 228mounted in apertures 230 provided in the side wall portions 232 of theisland 70 and are insulated therefrom by cylindrical inslators 234 whichare positioned in the apertures 230. The arm 74 includes a right housinghalf 234 and a left housing half 236 which are joined together by stovebolts 238 to encase the bus-bar 204. Free flow of air through the arm 74is assured by providing it with an open bottom 240 and a iinned top wall242 having a plurality of heat-radiating iins 244. The pivot pin 228 isconnected to the end 72 of arm 74 by a pair of hollow transition members246 which are mounted in a rectangular opening 2418 provided in the topwall 250 of the island 70 and which are provided with an opening 249through which the crook 206 extends. The members 246 each include abifurcated portion 252 which extends downwardly from the housing half 14into the lower housing half 16. The members 246 are connected togetherby a stove bolt 254 so that the bifurcated portions 252 form ,a U-shapedtrackway 256 for a dielectric roller 258 having a peripheral iiange 260engaged in a slot 262 for preventing lateral displacement of the roller258 as it is rolled along the trackway 256 by a crank 264 provided onthe end 266 of an operat- 188 (FIG. l1) to during use.

ing handle 268. The operating handle 268 includes another end 270 whichextends through the U-shaped openings 78 and 80. The end 270 carries agrip portion 274 adjacent which an aperture 276 is provided in theoperating handle 268 for the reception of one end 278 of a cord 280having its other end 282 attached to a treadle 284 for actuating theoperating handle 268 by a foot control 285.

The operating handle 268 includes a bight portion 286 which is pivotallymounted in the frame 114 in a pair of spaced, U-shaped notches, one ofwhich is shown at 288 in FIG. 6. The bight portion 286 is retained inposition in the notches 288 by the laminated portion 124 0f thetransformer 120. The operating handle 268 also includes a lever 289extending from the bight portion 286 to the grip 274 superadjacent anactuating button 290 extending upwardly from the switch 134. The oper-Iating handle 268 may be depressed to swing the arm 74 downwardly sothat the electrode 218 will engage the workpiece 187 with the ixedelectrode 170 with an optimum pressure, regardless of the thickness ofthe workpiece 187. This is accomplished by making the operating handle268 out of steel and forming the lever 289, the bight portion 286 andthe crank 264 integrally so that, when the lever 289 reaches the bottomof its stroke, it contacts button 290 actuating the switch 134completing a circuit to the transfermer 120. The switch 134 is aiixed toa plate 291 by screws 292 in a position sufficiently below the lever 289that the lever 289 must be sprung downwardly after the electrodes 218and have rmly clamped the workpiece 187. Thus, the amount the lever 189is sprung for thick workpieces is greater than the amount it is sprungfor thin pieces and, therefore, the operating handle 268 has a torsioneffect which results in approximately the same p.s.i. being applied to athick workpiece as that applied to a thin workpiece.

Although many uses for the spotwelder 10 will manifest themselves, it isprimarily a hobby tool for spotwelding wire shapes. During such weldingoperations, it is quite often desirable to cut and bend the wire. Forthis purpose, the end 52 of the cutter bar 48 may be inserted into therecess 46 with the notch 50 engaging the web 62 and the notches 54 and58 engaging the pads 64 and 66, respectively. The cutter bar 48 may thenbe wedged into position by a wedge assembly 294 having a grip portion296 and a wedge-shaped end 298. The end 298 is provided with a notch 299engageable with the web 62. A cutter handle 300, having a first end 301forming a grip portion and a second end 302, may then be assembled tothe cutter bar 48. This is accomplished by engaging a button 304,provided on the end 302 of the cutter handle 300, in a keyhole-typeaperture 306 provided in the cutter bar 48 adjacent its end 308 in such4a manner that a crook 310 formed in the end 308 will face a similarcrook 312 formed in the end 302 of the cutter handle 300. This forms asmall aperture 314 adapted to receive the wire workpiece 187 so that itmay be severed by pushing downwardly on the grip portion 301.

The workpiece 187 may be bent to various shapes by placing the bendingblock 44 into the square opening 42 in such a manner that a cylindrical,bifurcated member 316 provided on the bending block 44 extends above thetop wall 18. The cutter handle 300 may then be mounted on thecylindrical member 316 by engaging an aperture 318 provided thereinadjacent the button 304 with the cylindrical member 316 in such a mannerthat the button 304 is uppermost. The workpiece 187 may then be insertedinto the bifurcated portion 320 of the member 316 in such a manner thatthe end 322 of the workpiece 187 extends past the button 304. The handle300 may then be rotated bending the end 322 of workpiece 187 about thebending block 44.

Operation of the device will be readily understood. If the cord 280 andthe foot control 285 are not being used, the spotwelder 10 may be placedon a suitable level surture of internal parts of the welder face andplugged into a convenient 117 volt A C. house outlet. No other largeappliances should be operated at the same time on the circuit servicingthe spotwelder 10. If it is desired to use the foot control 285, thespotwelder 10 should be placed near the edge of a table so that the grip274 on the operating handle 268 extends over the edge of the table. Theend 278 of cord 280' may then be placed through the aperture 276 in theoperating handle 268 and down through the treadle 284. The treadle 284may then be adjusted to a convenient angle after which the end 282 ofthe cord 280 is tied off.

A cooling tray should then be lled with Water and, if desired, a spongemay be placed in the water.

The electrodes 170 and 218 may be cleaned by sanding them lightly withemery cloth. If it is desired to weld wire, steel wire up to 1/8 inchdiameter may be used. The areas to be welded should be cleaned withemery cloth and any non-conductive coating, such .as paint, rust or thelike, should be removed. The two parts to be welded together should becentered between the electrodes 170 and 218 Vafter which the controllever 268 may be pressed down to clamp the workpieces between theelectrodes. The lever 268 must be pressed down until it bottoms out inslot 80 so that the button 290 will be depressed closing the circuit tothe transformer 120. The control handle 268 is held in its down positionfor up to 2 seconds, depending upon wire sizes. The welding cycle startsonly when control lever 268 is pressed all the way down. The metal fromthe two wires will fuse together only after it is red hot. After theweld has been completed, the handle 268 may be released whereupon theresilience of bus-bar 204 will return the arm 74 lto its elevatedposition separating the electrodes 170 and 218. The workpiece may thenbe removed and cooled by placing it on the wet sponge in the tray.

The spotwelder 10 may also be used for welding steel sheets having athickness no greater than 0.015 inch. Such sheets may be welded bycleaning the areas to be welded with emery cloth. The areas to be weldedshould then be dimpled with a 16 penny common nail on a wood block. Thedimple is used to locate the weld on the lower electrode 170 after whichthe control handle 268 may be lowered to clamp the workpieces betweenthe electrodes 170 and 218 and to actuate the switch 134.

During a welding operation, or otherwise, should the secondary circuitbecome shorted, the circuit breaker 142 will open the primary circuit inless than one second. The circuit breaker also controls the maximumtemperato a maximum rise of 65 C. when the spotwelder 10 isoperated atmaximum rated duty cycle of 8%. In addition, the circuit breaker 142controls overloading, overheating and undesirable combinations of bothwithin stated maximum temperature and amp branch circuit limitations.

While the particular spotwelder herein shown and described in detail isfully capable of obtaining the objects and providing the advantageshereinbefore stated, it is to be understood that it is merelyillustrative of the presently preferred embodiment of the invention andthat no limitations are intended to the details of construction ordesign hereinshown other than as dened in the appended claims.

What is claimed is:

1. A miniature spotwelder, comprising:

a transformer 'having a primary winding and a secondary wind-ingr a xedWelding electrode connected lwinding;

a swingable Welding electrode;

a bus-bar connecting said swingable electrode to said secondary winding,said busabar having means comprising its physical properties and shapefor biasing said swingable electrode to a predetermined position spacedsuiiiciently from said fixed electrode to admit workpieces therebetween;and

a swingable lever connected to said bus-bar for swingto said secondarying said swingable electrode towards said xed electrode clamping saidxworkfpieces therebetween.

2. A spotwelder as started in claim 1 including mutually engageablespark arrestor means encompassing and shielding each of said electrodesat all times during a welding operation to prevent sparks from leavingthe welding area.

3. A spotwelder as stated in claim 1 including switch means controllingthe flow of electrical current to said primary iwinding, said switchmeans being mounted in lthe path of travel of said lever and beingspaced a predetermined distance from said lever at the end of itselectrodeclosing stroke, said lever including means comprising itsphysical properties an-d shape whereby said lever may be sprung intoengagement with said switch means to complete a circuit to said primarywinding only after said lever has been swung sufficiently to cause saidswingable electrode to exert `a predetermined pressure on saidworkpieces.

4. .A miniature spotwelder, comprising:

a transformer having a primary winding and a secondary Winding;

a fixed welding electrode connected to said secondary winding;

a swingable welding electrode;

a bus-:bar connecting said swingalble electrode to said secondarywinding, said bus-bar having suicient resiliency and a predeterminedshape for biasing said swingable electrode to a predetermined position`spaced sufficiently from said xed electrode to admit workpiecestherebetween;

a swingable lever connected to said bus-bar for swinging said swingableelectrode towards said fixed electrode clamping said workpiecestherebetween;

Ihousing means;

an electrical switch mounted in said lhousing means in a predeterminedposition, said switch completing a circuit to said primary winding, saidlever including a bight portion pivotally mounting said lever in saidhousing, a grip portion connected to one end of said bight portion andextending to the exterior of said housing for actuation by a user of`said spotwelder and a crank member extending from the other end of saidbight portion; and

means connecting said crank portion to said bus-bar, said leveractuating said switch when said grip portion has been swung apredetermined amount 'by said user, said predetermined position of saidswitch being such that said lever must be swung suiiciently after saidswingable electrode has clamped said workpieces against said fixedelectrode to cause .a predetermined pressure to be exerted on saidworkpieces.

5. A spotwelder as stated in claim 4 including an overload deviceconnected in said circuit between said switch and said primary winding.

6. A spotwelder as stated in claim 4 wherein said electrodes arethreadedly connected to said spotwelder, whereby said electrodes may bereadily removed with a wrench.

7. A spotwelder as stated in claim 4 including mutually engageable sparkarrestors, one surrounding each electro-de for shielding an associatedelectrode in such a manner that sparks emanating from said workpiecesare held captive and shielded from View, each of said spark arrestorsincluding a plurality of spun glass tufts having flat, looped portionswhich are deectible by said workpieces.

8. A spotwelder as stated in claim 1 wherein said busbar comprises ahard-drawn copper unit having a straight portion and a crook, saidstraight portion having a free end, an electrode holder straddling saidfree end, said electrode holder including an internally threadedportion, said swingable electrode including external threads orthreadedly engaging said internally threaded portion in suc-h a mannerthat one end of said swingable elecan actuating handle having a bightportion, a crank portion extending from one side of said bight portrodemay be threaded into rrn engagement with said free end, thereby clampingsaid electrode holder to said free end.

9. A miniature spotwelder, comprising:

a housing having an 4upper housing half and a lower 5 a free endextending externally of said housing, said housing half, said lowerhousing half including a operating handle `being pivotally mounted insaid ybottom w-all having an upstanding pedestal provided housing byengaging said bight portion between thereon, said upper housing halfincluding a top said transformer and said top wall, said leverextendwall having a plurality of posts depending therefrom ing along theunderside of said lever extending along toward said bottom wall; 10 theunderside of said top wall superjacent said a 'welding transformerconnected to said posts and exelectrical switch and being engagea-blewith said tending into said lower housing half, said welding button whensaid lever is depressed a predetermined transformer including a primarywinding connecti amount, said crank portion being connected to said ableto a 117 volt A.C. electrical current source -bifurcated portion forswinging said swingable arm and being designed to draw 12 amps at fullload, said 15 to lower said swingable electrode toward said fixedtransformer also including a secondary winding havelectrode when saidhandle is depressed, said button ing a secondary voltage ofapproximately 1 Volt at being located a suicient distance from saidlever 650 amps, said transformer converting 12 amps of portion that saidlever portion must be depressed the 117 volt A.C. current intoapproximately 650 suciently after said swingable electrode has engagedamps of approximately 1 volt welding current under 20 a workpieceagainst said xed electrode to exert a full load; predetermined pressureon said wonkpiece before ak swingable arm swingably connected to saidtop wall, said button is contacted; and l said swingable arm including abifurcated portion spark arrestor means surrounding said electrodes forextending through said top wall into said housing; confining sparksemanating from said workpieces to a hard-drawn copper bus-bar having oneend connected the area surrounding said electrode and for hiding to saidsecondary winding, a crook extending from said one end up through saidbifurcated portion and a straight portion extending from said crookthrough said arm, said straight portion including a free end tion and alever portion extending from the other side of said bight portion, saidlever portion having said sparks from the view of a user of said spot-Welder.

10. lIn combination with a spotwelder having upper and lower weldingelectrode means, spark arrestor means,

positioned at the free end of said arm; comprising:

a swingable electrode holder connected to said free yskirt meanssurrounding each of said electrode means, end of said bus-bar, saidswingable electrode holder each of said skirt means including an annularcollar including an internally threaded portion communiand a pluralityof heat-resistant, deformable elements eating with `said free end ofsaid bus-bar; affixed to said annular collar in overlapping relation anexternally threaded, swingable electrode threadedly and beingdeflectilble by a workpiece being welded engaging the internallythreaded portion of said by said electrode means while completelysurroundswingalble electrode holder and extending iuto clarnping theportion of said workpiece at said electrodes ing engagement :with saidfree end; by flexing around it.

a second #busebar having one end connected to said secondary winding anda free end extending through References Cited by the Examiner saihlusinbg toba position adjacent the free end of UNITED STATES PATENTSsal o er us-i ar; y

a xed electrode holder positioned on the free end of gllmson 219 86 elps219-110 X said second 'bus-bar, sald xed electrode holder 1n- 1 986 5121/1935 AMeadowcroft 219-86 cluding an lnternally threaded portioncommuni- 2 175 749 10/1939 Bckm t an 219-120 X catlng w1th said free endof sa1d second bus-bar; 2 194 573 3/1940 S chulz 219-86 a fixedelectrode having external thread threadedly en- 2,434,025 1/1948 Wallace219-86 gagmg sald internal threads on sald fixed electrode 268.8 06458/1954 Clark 219 86 holder and extending into clamped engagement withsaid free end of said second bus-bar;

an electrical switch connecting said primary circuit to a source of 117volt A.C. current, said switch including an actuating button located apredetermined distance below said top wall;

FOREIGN PATENTS 482,472 3/193'8 Great Britain.

RICHA-RD M. WOOD, Primary Examiner.

1. A MINIATURE SPOTWELDER, COMPRISING: A TRANSFORMER HAVING A PRIMARYWINDING AND A SECONDARY WINDING; A FIXED WELDING ELECTRODE CONNECTED TOSAID SECONDARY WINDING; A SWINGABLE WELDING ELECTRODE; A BUS-BARCONNECTING SAID SWINGABLE ELECTRODE TO SAID SECONDARY WINDING, SAIDBUS-BAR HAVING MEANS COMPRISING ITS PHYSICAL PROPERTIES AND SHAPE FORBIASING SAID SWINGABLE ELECTRODE TO A PREDETERMINED POSITION SPACEDSUFFICIENTLY FROM SAID FIXED ELECTRODE TO ADMIT WORKPIECES THEREBETWEEN;AND A SWINGABLE LEVER CONNECTED TO SAID BUS-BAR FOR SWINGING SAIDSWINGABLE ELECTRODE TOWARDS SAID FIXED ELECTRODE CLAMPING SAIDWORKPIECES THEREBETWEEN.